1. Field of the Invention
The invention relates to a method and apparatus for spirally winding a magnetic core from at least one filament of magnetic material. More particularly, the invention relates to a method and apparatus for winding a transformer core from at least one filament of magnetic material composed of a glassy metal alloy.
2. Description of the Prior Art
When manufacturing a power transformer core using conventional magnetic material, the core has ordinarily been comprised of individual sheets of material which have been cast or stamped into a preselected planform shape. The formed sheets are laminated to build up the thickness of magnetic material needed to provide a core body of the desired configuration.
Glassy metal magnetic alloys are especially desirable for use in transformer cores because of their improved magnetic characteristics such as high permeability, low core power loss, and low VA (volt-ampere) characteristics. Glassy metal magnetic alloys, however, are tougher and harder than conventional crystalline magnetic alloy materials, and cannot be easily stamped or cut to form the required shapes. In addition, such alloys are necessarily produced in thin strips or ribbons because of the rapid quench rates needed to develop amorphous, glassy metal structures. As a result, the most efficient means of building up a core body is by spirally winding a filament of magnetic material into successive, multiple laminations. Since the filaments of glassy metal alloys are generally less than six centimeters wide, multiple, individually wound core elements are needed to build up the material volume needed to produce the desired cross-sectional shapes for larger transformer cores wider than six centimeters. In addition, glassy metals generally have a low coefficient of friction and mated surfaces slide easily over one another. Therefore, it has been difficult to prevent relative motion between the multiple, juxtaposed wound elements, which can distort the core configuration during and after the winding operation. The core distortions, in turn, induce undesired stresses that degrade the magnetic characteristics. Thus, due to the particular physical characteristics of glassy metal magnetic alloys, conventional methods and apparatus have produced distorted power transformer cores with degraded magnetic characteristics.